To further improve a capacity and spectrum efficiency of a wireless communications system, so as to meet a user's requirement for a wireless access capacity, a wireless communications access system further develops towards a dense network structure, broader bandwidth, and higher spatial multiplexing, so that a future high-speed wireless access requirement can be met. A microwave band or millimeter-wave frequency band has abundant spectrum resources and attracts increasing attention from communications device manufacturers. However, space loss is large. Therefore, a large-scale antenna array is used to reduce the space loss and improve a system capacity and frequency spectrum efficiency. In a microwave or millimeter-wave wireless communications system that has large-scale antennas, a hybrid beamforming system of digital precoding and analog weighting is also used, so as to reach an optimal compromise between performance and system complexity.
Currently, for the hybrid beamforming system, commonly used beam tracking methods are mainly a scanning method and a real-time calculation method. In the scanning method, scanning is mainly performed by changing a weighted value of a phase shifter to change a beam direction, and a receive end selects an optimal communication beam according to a maximum receive power criterion. In the real-time calculation method, channel decomposition and matching are mainly performed according to a channel estimated in real time, and a weighted matrix of a radio-frequency end and a weighted matrix of a digital end are jointly calculated.
In existing beam tracking methods, the scanning method is relatively simple and is applicable to a LOS (line-of-sight) propagation scenario, and the method can have approximately optimal performance in the LOS propagation scenario. However, the scanning method is inapplicable to an NLOS (non-line-of-sight) propagation scenario. The real-time calculation method is applicable to the NLOS propagation scenario and the LOS propagation scenario, and the real-time calculation method has optimal performance in the NLOS propagation scenario. However, because there are a relatively large quantity of antennas in a high-frequency large-scale antenna system, if a channel is estimated in the real-time calculation method by using a conventional pilot-based solution, a large quantity of timeslots need to be occupied to send a training sequence. In addition, because a dimension of a channel matrix in the high-frequency system is large, many resources need to be occupied to feed back channel information, and consequently, the method is difficult to implement.